1. Field of the Invention
This invention relates generally to adjustable, pressure compensated, restrictive flow regulator valves, and more particularly to a restrictive flow regulator cartridge having improved pressure compensation.
2. Description of the Prior Art
Restrictive flow regulator valves are widely used in the fluid power industry in applications where speed control, independent of pressure drop, is required. Speed control is achieved when the unit flow through the valve in terms of volume per time period remains constant.
In its simplest form, a valve of this type consists of a flow control orifice, a compensating spool and a control spring, all contained in a suitable housing or valve body. Flow through the valve from port A (the inlet port) to port B (the outlet port) creates a pressure drop across the orifice. The magnitude of the pressure drop for a given flow control orifice opening depends, primarily, upon the flow rate. This pressure drop is applied across the compensating spool and tends to cause it to move in a direction to restrict flow through port B, the outlet port. This tendency of the spool to move to restrict flow is opposed by the control spring. Ideally, the flow will not be restricted by the spool until it has reached a high enough rate so that the force due to the pressure drop is greater than the control spring force. At this time the spool should move to restrict flow and maintain a constant pressure drop across the orifice.
A problem associated with currently available valves of this type is that before flow begins they are normally open because the force applied by the control spring against the compensating spool is unopposed. At the start of flow, the only resistance to flow is that afforded by the flow control orifice. As a result there is an initial surge in fluid flow until, after a finite time, the force due to the pressure drop takes effect, causing the spool to shift against the control spring and regulate the pressure drop across the orifice. This initial surge is an undesirable effect in a valve which is intended to provide a controlled and constant flow rate at all times.
It is therefore an object of this invention to provide a restrictive flow regulator valve in which control of flow is provided from the moment pressure is applied.
It is also an object of this invention to provide a pressure compensated restrictive flow regulator valve in a cartridge form.
It is a further object of this invention to provide a pressure compensated restrictive flow regulator valve which may be fully adjusted to a desired flow rate between shutoff and full open maximum.
It is also an object of this invention to provide a pressure compensated restrictive flow regulator valve which is of a normally closed configuration.
It is also an object of this invention to provide a pressure compensated restrictive flow regulator valve having a free reverse flow configuration.